Flying a 10cc Evo gasser in a similar size, weight and power plane (.46 Phoenix Extra). Good sport performance, but not close to 3D.
The 15cc engine weighs nearly what a DLE 20 weighs (all up), so even if you did have more power than the 10cc plane, the wing loading would be well into what the military guys are flying. Basically something you need to be pretty careful with at lower speeds - snap happy.
The 10 is the way better plan for most flyers IMHO. Be interested in your impressions when you get it together. Please keep us posted! -Al